1. Field of the Invention
This invention relates to water hammer arresters; i.e. to devices for preventing the development of water hammer in conduits conveying water under pressure and under conditions of interrupted flow.
2. Description of the Prior Art
The familiar phenomenom of water hammer is caused by the development of hydraulic shock waves generated by the sudden stopping of fluid flow within the confines of a conduit system carrying water under pressure. This condition results from the rapid closing of positive valves incorporated within the system. In addition to the production of unpleasant noise effects, fluid hammer if allowed to persist for any length of time, will result in broken conduits and damage to other components of the conduit system.
Various types of fluid hammer arresters are known to the prior art. The most commonly employed of such devices includes expandable bellows or diaphragms which absorb the shock. These are so subject to failure that their service life is short.
Another type of fluid hammer arrester involves the application of a piston working against the pressure developed by a compressed gas chamber. Such a device is disclosed in Perrott et al, U.S. Pat. No. 3,633,627. Although widely and successfully used, water hammer arresters of the Perrott et al class are characterized in use by a noise generating problem. When subjected to rapid and substantial pressure drop, the metallic piston with which they are provided occasionally forcibly contacts an opposed metallic wall. This causes the production of an unpleasant metallic sound, or "ping". The arresters accordingly defeat their own purpose in that they themselves become a sound-producing instrument.
It is the general purpose of the present invention to provide a water hammer arrester which overcomes this problem, and which is ping-free.